How can a someone completely unrelated be the best match fora kidney or bone marrow?
In: Biology
Organ donors need to match a few key types to be a strong match: blood type, crossmatching, tissue typing, similar size, etc. There is some variance within each of these, but not an enormous amount. And while siblings and close relatives are more likely to share these types (due to sharing more DNA), it’s not super rare for these cases to match between strangers – it’s just less common than among siblings.
To make a similar example, my brother and I both have brown hair, green eyes, and we’re within an inch or so in height. If you look in our immediate family, you’ll find a few other people who match those traits, and a few who won’t (like our sister, who has red hair). If you start to look outside of our family, you’ll find fewer people that match on those traits, but if you look for a little while, you’ll still eventually find matches; they just aren’t as common as they were within our immediate family. It’s similar with these other genetic matches: uncommon between strangers, but if you are able to check a large group of people, some close matches will turn up, because there are only so many possible traits.
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